Steroid/thyroid receptors play a crucial role in development, differentiation and maintenance of homeostasis in diverse species. The recent molecular cloning of many of the members of this supergene family has led to rapid expansion of research activities in this field and a considerable increase in our basic understanding of how these ligand-dependent transcription factors regulate gene expression. The development of efficient expression systems has now permitted the production of sufficient quantities of these receptors for analysis of in vitro gene transcription and for physical-chemical studies. The major problems facing the field of molecular endocrinology today are to understand the precise details of how steroid-thyroid receptors interact with DNA and other transcription factors to control gene expression, and to define the precise roles of receptor associated proteins (heat shock, etc.) and post transcriptional modification (phosphorylation) on receptor function. Comprehension of hormone action will require a complete understanding of the regulation of receptor gene expression and the role of receptors during development. The proposed program will facilitate addressing these issues by bringing together the foremost authorities on the steroid-thyroid receptor supergene family for the first time since the cloning of the genes. Additionally, we seek support to encourage participation of young scientists in early stages of their career development (graduate students, postdoctoral fellows, assistant professors) who will be future contributors to this important area of medical sciences. Interaction of these young investigators with established leaders in the field should provide an environment that will result in significant scientific discoveries. In the organization of this meeting, we will also take a unique comparative approach to each topic so as to permit optimal communication among researchers studying various members of the supergene families. Such a meeting should set the stage for the next era of research on these important regulatory molecules.